/Engine/Source/Runtime/Engine/Classes/Engine/Texture.h
Optional extra fields for texture platform data required by some platforms. Data in this struct is only serialized if the struct's value is non-default.
struct FOptTexturePlatformData
uint32
ExtData
Arbitrary extra data that the runtime may need.
uint32
NumMipsInTail
Number of mips making up the mip tail, which must always be resident